Life on Earth may have started thanks to a modified version of RNA


DNA is the backbone of life and almost all of our planet depends on it but, on primordial Earth, a primitive version of its lesser-known sister – RNA – was the focal point for evolution, scientists have discovered.  

RNA is structurally similar to DNA, except one of the four fundamental pieces, thymine, is substituted for uracil. 

This changes the shape and structure of the molecule and scientists have long believed this chemical to be the cause of Earth’s first lifeforms. 

An accidental discovery by Harvard academics has now found that a slightly different version of RNA may have been the key ingredient allowing for life on Earth to blossom.   

Scientists claim that a chemical called inosine may have been present in place of guanine, allowing for life to develop.  


This slight change to the bases, known as a nucleotides,  may provide the first known proof of the ‘RNA World Hypothesis’ – a theory which claims RNA was integral to primitive lifeforms. 

Jack Szostak, a professor at Harvard University, along with first-author and graduate student Seohyun Kim, suggest RNA used inosine as a surrogate. 

‘Our study suggests that the earliest forms of life (with A, U, C, and I) may have arisen from a different set of nucleobases than those found in modern life (A, U, C, and G),’ said Mr Kim.  

Lab attempts to craft adenine and guanine, purine-based nucleotides that bond with thymine/uracil and cytosine, respectively in DNA/RNA failed when using what was available on primordial Earth. 

Issues stemmed from the reaction producing to many undesirable side-products. 

Inosine enabled RNA to replicate with high speed and few errors, a feature which is essential for reproduction.

Researchers said: ‘[It] turns out to exhibit reasonable rates and fidelities in RNA copying reactions.

‘We propose that inosine could have served as a surrogate for guanosine in the early emergence of life.’  

Professor Szostak and Mr Kim’s discovery could help substantiate the RNA world hypothesis. In time, their work might confirm RNA’s primary role in our origin story. 

Eventually, armed with this knowledge, scientists may be able to identify other planets that have the essential ingredients and determine whether we share this universe or are, indeed, alone. 

The research was published in the journal Proceedings of the National Academy of Sciences. 


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